Scotland lock Jim Hamilton will replace Steve Borthwick in Saracens' engine room next season after completing his switch from French Top 14 side Montpellier.
The former Edinburgh and Leicester second row left Gloucester for Montpellier last summer on a lucrative three-year deal, but will return to England after just one season in France.
Saracens view the 31-year-old enforcer and line-out coordinator as the ideal replacement for captain Borthwick, who will retire after Saturday's Aviva Premiership final following a 16-year top-flight career.
"Jim Hamilton is one of the most respected lock forwards in the game, a big man with a big presence on and off the field," said Saracens rugby director Mark McCall.
"He was courted by several leading European clubs, and we are delighted he has chosen to join Saracens."
Saracens have completed a double raid from Montpellier by bringing Argentina prop Juan Figallo to Allianz Park, to replace Sharks-bound Matt Stevens.
Saracens boss McCall believes the 22-cap 26-year-old already rates among the best tighthead props in the world.
"Juan Figallo was ranked as the world's number one tighthead prop last year and will prove a massively significant signing," said McCall.
"He has almost completed rehab following a neck injury and will be ready for the start of the new season."
England Sevens wing Mike Ellery has also agreed a deal to join Saracens next season, the club have announced.
The 24-year-old Newcastle Falcons academy graduate impressed in Moseley's back-row at Championship level, before joining England Sevens in 2012.
Saracens boss McCall believes the former Westoe and Darlington Mowden Park forward can now transfer his short-format success to both Premiership and European competition.
"Mike Ellery is a tall, strong man with both skill and speed," said McCall.
"He has been making headlines on the Sevens circuit, and we are looking forward to helping him realise his full potential in the 15-man game."